Copolyamides

ABSTRACT

The invention relates to semi crystalline, melt processible, partially aromatic copolyamides, producible by condensation of at least the following monomers or the precondensates thereof: a) terephthalic acid b) at least one dimerised fatty acid with up to 44 carbon atoms and 
         c) at least one aliphatic diamine of the formula H 2 N—(CH 2 ) x —NH 2 , wherein x means a whole number from 4-18.

The present invention relates to semi crystalline, melt processible,partially aromatic copolyamides which, in addition to terephthalic acidand at least one aliphatic diamine H₂N—(CH₂)_(x)—NH₂ with x=4-18, alsocontain at least one dimerised fatty acid with up to 44 carbon atoms andif necessary further aromatic dicarboxylic acids, aliphatic dicarboxylicacids and lactams or co-aminocarboxylic acids and which, due to thisselection of components, are endowed with increased toughness relativeto comparable partially aromatic copolyamides.

Semi crystalline, partially aromatic copolyamides with hexamethyleneterephthalamide units in addition to other amide units were introducedon the market approximately twelve years ago and since then have beenpart of engineering thermoplastics. Thanks to their high melting pointsof up to approx. 330° C., these products in the form of their glassfibre-reinforced compounds are distinguished by very highthermostability (HDT Heat Distortion Temperature). In addition, theseproducts are also resistant to many aggressive chemicals, even atcomparatively high temperatures, which makes them, together with theirhigh HDT values, suitable for applications which can no longer berealized with conventional polyamides, e.g. PA6 or PA66.

These products, for which in the meantime the generally accepteddescription “polyphthalamides” has been established, are described indetail—sometimes also the production methods—in numerous printed patentspecifications, for example in U.S. Pat. No. 4,603,166, U.S. Pat. No.4,831,108, U.S. Pat. No. 5,098,940, U.S. Pat. No. 5,302,691, WO90/02017, WO 92/10525, WO 95/01389, EP 0 360 611 B1, EP 0 449 466 B1, EP0 550 314 B1, EP 0 550 315 B1, EP 0 693 515 B1 and DE 43 29 676 C1.

The overall excellent properties of the polyphthalamides should howevernot conceal the fact that there is a significant requirement forimprovement in the case of some of their properties. In particular thetoughness of these products, expressed by their impact strength andnotched impact strength, and often also their elongation at break, doesnot fulfil all requirements.

It is therefore the object of the present invention to provide novelsemi crystalline, melt processible, partially aromatic copolyamides withincreased toughness. As a second object of the invention, the polymerstructure of these products is intended thereby to be modified such thatno change is necessary in the production method, i.e. the partiallyaromatic copolyamides according. to the invention can be producedaccording to the known methods of the state of the art. This object isachieved by the semi crystalline, melt processible, partially aromaticcopolyamides according to claims 1 to 13, which can be used according toclaim 14 for producing moulded parts by means of melt processingmethods.

This object is achieved with copolyamides which have been obtained fromspecific selected monomers or precondensates thereof. In addition toterephthalic acid (component a), at least one dimerised fatty acid b)with up to 44 carbon atoms is used and at least one aliphatic diamine ofthe formula H₂N—(CH₂)_(x)—NH₂ (component c), wherein x means a wholenumber from 4-18. If necessary, further monomers d), e) and f) (claims 2to 5) are used. The obtained copolymer preferably has a melting point ofat most 335° C., measured by means of DSC.

The above-described monomers, educts a)-c) if necessary with d)-f), arethereby used in such molar ratios which lead to end products which aresemi crystalline and have a melting point by means of DSC which is atmost 335° C.

The individual monomers are described in more detail subsequently.

The dimerised fatty acids b) are obtained from monomer unsaturated fattyacids with preferably 18 carbon atoms by a specific oligomerisationreaction. As a result of this reaction, smaller quantities of thetrimerised fatty acid are produced in addition to an unsaturateddimerised one. By subsequent catalytic hydration, the C—C double bondscan be removed. The term “dimerised fatty acid”, as it is used here,relates to both types of these dicarboxylic acids, saturated andunsaturated. Details relating to the structure and the properties of thedimerised fatty acids are found in the corresponding leaflet “PripolC₃₆-Dimer acid” of the Company UNICHEMA (Emmerich, D) or in the brochureof the Company COGNIS (Düsseldorf, D) “Empol Dimer and Poly-basic Acids;Technical Bulletin 114C (1997)”. In order to produce polyamides,dimerised fatty acids with a content of trimerised fatty acid of at most3% by weight are used. There are a lot of polyamides of this type whichgenerally melt at a very low temperature or have absolutely no meltingpoint, are highly flexible to rubber-like and are used to produceflexible products, such as binders, shoe adhesive and adhesive films. InCA 861 620, products of this type are described for example. Only a fewpartially aromatic copolyamides modified with dimerised fatty acids areknown, which have high rigidity and strength. Products of this type aredescribed for example in U.S. Pat. No. 5,177,178, this howeverconcerning amorphous copolyamides which, in addition to a dimerisedfatty acid, contain an aromatic dicarboxylic acid and at least onecycloaliphatic diamine. The function of the dimerised fatty acid is herereducing the water absorption of these amorphous copolyamides and oflimiting the reduction in the glass transition temperature associatedwith the water absorption (see column 2, lines 18-23 and 48-54). It isasserted in column 4, lines 4-5 that the amorphous copolyamides weredistinguished by high impact strength (“. . . high . . . impactresistance.”). In fact, examination of the impact strength and notchedimpact strength (measuring methods: see below) of the product accordingto example 1 just produced values of 27 and 0.5 kJ/m², which is similarto a pronounced brittle breaking behaviour and does not at all fulfilthe lowest requirements. EP 0 469 435 B1 likewise claims amorphouscopolyamides which contain dimerised fatty acids, which copolyamidesdiffer from the products of U.S. Pat. No. 5,177,178 in the structure ofthe cycloaliphatic diamine which is used. In impact strength and notchedimpact strength, the behaviour here is not very different from U.S. Pat.No. 5,177,178. The notched impact strengths of the copolyamides ofexample 3 and 4 are indicated by 0.7 and 0.6 kJ/m², the impact strengthof example 4 by 35.3 kJ/m². Finally, U.S. Pat. No. 5,177,178 and EP 0469 435 B1 say nothing about the possible effects of dimerised fattyacids as a component of semi crystalline, partially aromaticcopolyamides. The latter is also true for U.S. Pat. No. 5,708,125 whichin fact accepts dimerised fatty acids as cocomponents of precondensatesof amorphous or semi crystalline, partially aromatic copolyamides butcontains neither such examples nor any details about the properties ofpossible polymer end products.

Component c) concerns aliphatic diamines of the formulaH₂N—(CH₂)_(x)—NH₂, wherein x means a whole number from 4-18. Preferably,the copolyamides according to the invention contain hexamethylenediamine, 1,9-diaminononane, 1,10-diaminodecane or 1,12-diaminododecane.

If necessary, the copolyamides according to the invention can contain afurther aromatic dicarboxylic acid d), an aliphatic dicarboxylic acid e)and a lactam or a co-aminocarboxylic acid f) with 6-12 carbon atoms,there being preferred isophthalic acid for d), adipic acid for e) andlaurinlactam or ω-aminolauric acid for f).

The melting point of the copolyamides according to the invention is atmost 335° C. and, for the copolyamides defined in claims 7, 8, 9 and 10,it is at least at the temperatures indicated there.

The present invention relates to partly aromatic copolyamides which arenot however semi crystalline over their entire composition range andconsequently do not always have a melting point. It is thereforeappropriate to indicate criteria which make it possible to differentiatebetween semi crystalline and amorphous copolyamides and in addition toindicate the melting point of the semi crystalline products. In the caseof amorphous polyamides, e.g. the article “Structure PropertyRelationship in Amorphous Polyamides” by J. G. Dolden, which appeared inPolymer 1976, Vol. 17, pages 875 to 892, offers valuable assistance inthis respect. The prediction of semi crystallinity of partially aromaticcopolyamides is definitely possible at least for the group of so-calledisomorphous copolyamides. Examples of systems of this type are PA-66/6T,PA-46/4T, PA-106/10T and PA-68/6PBDA based on hexamethylene diamine(HMD)/adipic acid (ADA)/terephthalic acid (TPA) or tetramethylenediamine/ADA/TPA or decamethylene diamine/ADA/TPA and HMD/subericacid/p-benzene diacetic acid (PBDA). More detailed information in thisrespect can be found in numerous publications, e.g. in H. Plimmer et al.in the Brit. Pat. Appl. 604/49, Imperial Chemical Industries Ltd.(1949); R. Gabler, CH-A-280 367, Inventa AG (1949); M. Levin and S. C.Temin, J. Polym. Sci. 49, 241-249 (1961); T. Sakashita et al. in U.S.Pat. No. 4,607,073, Mitsui Petrochemical Industries Ltd. (1985); S.Yamamoto and T. Tataka, EP 0 449 466 B1, Mitsui Petrochemical Industriesand also in Brit. Pat. Appl. 766 927, California Research Corporation(1954). Information regarding non-isomorphous copolyamides, which canhave amorphous structures in specific ranges of their composition, arefound in some of the above publications and in A. J. Yu and R. D. Evans,J. Am. Chem. Soc., 20 5261-5365 (1959) and also F. B. Cramer and R. G.Beamann, J. Polym. Sci., 21, 237-250 (1956).

If on the basis of the above-cited publications and further works citedtherein no conclusive answer is possible as to whether a givencopolyamide is semi crystalline or amorphous or which melting point ithas, then a pre-test for producing the relevant product in a smalllaboratory autoclave is of further assistance. For this purpose, therespective components are mixed together with water and heated in theclosed autoclave after purging with an inert gas. After reaching 200 to230° C. product temperature, water vapour is withdrawn by opening thegas discharge valve and the pressure is reduced to ambient pressure withfurther heating to 250 to 290° C. However, it must thereby be taken intoaccount that, in the course of this procedure, higher meltingcopolyamides in specific operational states can crystallisespontaneously and can jam the agitator. The relevant product is removedfrom the autoclave and examined with respect to its melting point bymeans of differential scanning calorimetry (DSC). The DSC measurement isrepeated expediently once to twice on one and the same sample in orderto ensure a defined thermal previous history of the respectivecopolyamide. In the simplest case, instead of an autoclave, also astirable vessel which can be made inert and is operated withoutpressure, e.g. a glass flask, can be used to implement the pre-test. Thetemperature at the end of the reaction should thereby be likewisebetween 250 to 290° C.

The above-mentioned publications in fact relate only to products withoutdimerised fatty acids but nevertheless quite precise predictions can bemade from their melting points regarding the melting behaviour of thecorresponding copolyamides which contain up to approx. 30% by weight ofdimerised fatty acids.

It has in fact been shown that dimerised fatty acids in partly aromaticcopolyamides produce a surprisingly low depression of the melting pointand only slightly impair the crystallisation behaviour. Hence, a meanswas provided with the dimerised fatty acids with which not only thetoughness of semi crystalline, partially aromatic copolyamides isincreased, but also their melting- and crystallisation behaviour(solidification temperature and solidification speed at a given coolingrate) is extensively retained.

In this particularly favourable property combination, the copolyamidesaccording to the invention are significantly superior to thecopolyamides based on terephthalic acid, hexamethylene diamine andlaurinlactam described in EP 0 550 314 B1 and EP 0 550 315 B1. In orderthat these PA-6T/12 formulations can be made sufficiently tough, theymust contain at least 55% by mol PA-12 units. At this composition, themelting point is however only 245° C. and the solidification speed iscomparatively low.

In order to control their molecular weight, the copolyamides accordingto the invention can of course contain small quantities of aliphatic,cycloaliphatic or aromatic monocarboxylic acids and/or monoamines whichare added to the components before or during polycondensation. Theirproduction takes place according to known methods, as are described forexample in U.S. Pat. No. 4,831,108, U.S. Pat. No. 5,098,940, U.S. Pat.No. 5,708,125, EP 0 550 315 B1 or DE 4,329,676 C1.

Furthermore, it is possible to further modify the copolyamides accordingto the invention in different ways according to their respective use.Thus, in the case of copolyamides which are converted by melt processingmethods, such as injection moulding, injection moulding welding,extrusion, coextrusion, blow moulding, deep drawing and comparableprocessing methods to form corresponding objects, the addition ofreinforcing agents and fillers, such as glass fibres, carbon fibres,minerals (inter alia layered silicates) and other modifying agents, forexample heat stabilisers, UV stabilisers, antistatic agents, flameretardants, lubricants or mould release agents, is current practice.With respect to the mentioned melt processing methods, also thefollowing variants should be mentioned: production of hard-softcombinations, e.g. by injection moulding or extrusion, sequentialcoextrusion (e.g. according to EP 0 659 534 B1), sequential extrusionblow moulding (e.g. according to EP 0 659 535 B1), 3D blow moulding,coextrusion blow moulding, coextrusion 3D blow moulding, coextrusionsuction blow moulding, injection moulding with internal gas pressuretechnology (GIT) and internal water pressure technology (WIT). In thecase of heat and WV stabilisation, one can fall back on the methods andadditives inter alia as are described in DE 195 37 614 C2 or EP 0 818491 B2. The copolyamides according to the invention can furthermore bemixed with other polymers, e.g. other semi aromatic or aliphaticpolyamides, e.g. PA12 or PA66 or with polyolefins which are providedwith polar or reactive groups, such as e.g. carboxyl groups, anhydridegroups, imide groups or glycidyl(meth)acrylate groups. Thesefunctionalised polyolefins concern in particular copolymers with (i) amonomer of ethylene or a-olefin or if necessary a diolefin and (ii) atleast one comonomer which is selected from vinyl esters, saturatedcarboxylic acids, unsaturated mono- and dicarboxylic acids, the estersand salts thereof, and also dicarboxylic acid anhydrides (preferablymaleic anhydride). The functionalised polyolefins act inter alia asviscosity modifiers. The starting point for functionalised polyolefinsis e.g. polyethylenes (HDPE, LDPE, LLDPE), ethylene/propylene-,ethylene/1-butene copolymers, EPM, EPDM, SBS, SIS and SEBS.

The production of the copolyamides according to the invention ispossible by known methods. Reference is made by way of representation toU.S. Pat. No. 5,708,125 and U.S. Pat. No. 4,831,108.

Furthermore, the invention relates to moulded parts produced from orwith copolyamides as described above. It has proved to be particularlysuitable to use the copolyamides for hard-soft combinations.

EXAMPLES

The following examples explain the invention. All the products wereproduced according to a multi-stage method. The precondensate productionwas implemented according to the method described in U.S. Pat. No.5,708,125, the postcondensation in the melt corresponded inter alia tothe method described in U.S. Pat. No. 4,831,108.

In the first step, an aqueous solution of the components with 20-30% byweight of water is produced firstly at 190° C. in an agitated pressurevessel (V=20 l) which can be made inert with nitrogen. Agitation takesplace for two hours at this temperature until a pressure of approx. 1.0MPa has been set. After completion of this step, the solution iswithdrawn from the receiving vessel under pressure into a 20 l agitatedautoclave and heated there to 260° C., the pressure being maintained at3.3 MPa by means of repeated opening of a gas discharge valve. As soonas the pressure remains constant after approximately 2 hours—evenwithout further actuation of the valve—the base valve is opened and theprecondensate solution is withdrawn and sprayed into a cyclone. A largepart of the water thereby evaporates and irregularly formed particles ofthe relevant precondensate are obtained, which are dried in a vacuum at80° C. and subsequently ground into a powder.

In order to produce high molecular copolyamides, the precondensates arepostcondensed in the melt in a parallel twin-screw extruder of the ZSK25 type (product of the company Werner & Pfleiderer; Stuttgart, D) underthe following conditions. The highly viscose polymer melt is withdrawnas a strand, cooled and granulated

-   -   precondensate dosage and throughput: 4 kg/h    -   screw speed of rotation: 100 rpm    -   temperatures (zone 1-12):    -   30/40/ 100/300/350/370/370/370/370/370/360/330 and 330° C.    -   degassing: zone 10 under N₂    -   drying of the granulate: 24 hours at 100° C. in a vacuum.

The solution viscosity of precondensate and finished copolyamide wasdetermined in 0.5% by weight solution in m-cresol at 20° C. Thedetermination of the end group concentrations was effected by means ofacidimetric titration. The amino end groups were titrated inm-cresol/isopropanol 2:1 (weight-parts) as solvent with 0.1 normalethanolic perchloric acid. The titration of the carboxyl end groups waseffected in an orthocresol/benzyl alcohol mixture as solvent with 0.1normal tert-butylammonium hydroxide.

The DSC measurements were implemented with the appliance of the companyTA Instruments, Universal Type V2.3C.

In order to measure the Young's modulus and the elongation at break,tension tests were implemented according to ISO 527 on injection mouldedtension bars. The measurement of impact strength or notched impactstrength was implemented according to ISO 179/2-1 eU or ISO 179/2-1 eAon injection moulded test bars.

The abbreviations used in the examples have the following meaning: TPAterephthalic acid HMD hexamethylene diamine P1012 Pripol 1012 (= C₃₆dimer acid) IPA isophthalic acid ADA adipic acid ALA ω-aminolauric acidNHP sodium hypophosphite (NaH₂PO₂) DW Deionised water RV relativesolution viscosity in 0.5% solution in m-cresol at 20° C. [C] carboxylend group concentration in meq/kg [A] amino end group concentration inmeq/kg MP DSC melting point (° C.) IS impact strength at 23° C. in kJ/m²NIS notched impact strength at 23° C. in kJ/m² YM Young's modulus EBElongation at break in %

TABLE 1 Formulations TPA HMD P1012 IPA ADA ALA NHP DW [% by [% by [% by[% by [% by [% by [% by [% by Example wt.] wt.] wt.] wt.] wt.] wt.] wt.]wt.] Comp. 1a) 28.60 29.15 12.25 0.02 29.99 Comp. 2b) 23.10 30.23 16.620.02 30.03 Comp. 3c) 20.36 14.66 34.95 0.02 30.00 1 23.77 26.09 12.419.14 0.02 28.57 2 21.03 28.59 6.80 14.99 0.02 28.57 3 21.10 19.00 18.1511.71 0.02 30.01a)according to EP 0 360 611 B1 (MITSUI)b)according to EP 0 449 466 B1 (MITSUI)c)according to EP 0 550 314 B1 (ELF ATOCHEM S.A.)

TABLE 2 Relative viscosities, end groups and DSC melting pointsPrecondensate Copolyamide Example RV [A] [C] RV MP Comp. 1 1.137 — —1.91 330 Comp. 2 1.125 — — 1.93 315 Comp. 3 1.122 1410 1247 1.87 248 11.107 1588 1378 1.82 323 2 1.141 1184 1010 1.98 305 3 1.119 1470 12971.84 294

TABLE 3 Mechanical properties of the copolyamides in the dry stateExample IS NIS YM EB Comp. 1 58 4 3900 2 Comp. 2 97 5 4000 3 Comp. 3 40%w.b. 7 3300 5 1 60% w.b. 10 3100 4 2 w.b. 10 3060 6 3 w.b. 12 2700 9w.b.: without break

1. Semi crystalline, melt processible, partially aromatic copolyamides,producible by condensation of at least the following monomers orprecondensates thereof: a) terephthalic acid b) at least one dimerisedfatty acid with up to 44 carbon atoms and c) at least one aliphaticdiamine of the formula H₂N—(CH₂)_(x)—NH₂, wherein x means a whole numberfrom 4-18.
 2. Copolyamides according to claim 1, wherein the meltingpoint of these copolyamides, measured by means of DSC (DifferentialScanning Calorimetry), is at most 335° C.
 3. Copolyamides according toclaim 1, wherein a further aromatic dicarboxylic acid d) with 8-12 Catoms is present.
 4. Copolyamides according to claim 1, wherein inaddition an aliphatic dicarboxylic acid e) with 6-18 C atoms is present.5. Copolyamides according to claim 1, wherein in addition a lactamand/or an aminocarboxylic acid with 6-12 C atoms, preferableω-aminolauric acid, are present as further monomers f).
 6. Copolyamidesaccording to claim 1, wherein the aromatic dicarboxylic acid d) isisophthalic acid.
 7. Copolyamides according to claim 1, wherein thealiphatic dicarboxylic acid e) is adipic acid.
 8. Copolyamides accordingto one of the claims 1 to 7 claim 1, wherein in addition to the monomersa), b) and c) wherein x=6, isophthalic acid d) is present and themelting point of these copolyamides, measured by means of DSC, is atleast 290° C.
 9. Copolyamides according to claim 1, wherein in additionto the monomers a), b) and c) wherein x=6, adipic acid e) is present andthe melting point of these copolymers, measured by means of DSC, is atleast 270° C.
 10. Copolyamides according to claim 1, wherein in additionto the monomers a), b) and c) wherein x=6, isophthalic acid d) andadipic acid e) is present and the melting point of these copolyamides,measured by means of DSC, is at least 265° C.
 11. Copolyamides accordingto claim 1, wherein in addition to the monomers a), b) and c) whereinx=6, laurinlactam (f) or ω-aminododecanoic acid (f) is present and themelting point of these copolyamides, measured by means of DSC, is atleast 255° C.
 12. Copolyamides according to claim 1, wherein x=9, 10 or12.
 13. Copolyamides according to claim 12, wherein in addition to thecomponents a), b) and c), adipic acid (e) is present.
 14. Use of thecopolyamides according to claim 1, for the production of mouldedarticles by means of melt processing methods.
 15. Use of thecopolyamides according to claim 14, hard-soft combinations beingproduced as moulded articles.
 16. Use of the copolyamides according toclaim 14, the processing method being selected from extrusion, injectionmoulding, coextrusion, blow moulding, deep drawing, sequentialcoextrusion, sequential extrusion blow moulding, 3D blow moulding,coextrusion blow moulding, coextrusion 3D blow moulding and coextrusionsuction blow moulding.
 17. Moulded article produced from or withcopolyamides according to claim
 1. 18. Moulded article according toclaim 17, wherein it is a hard-soft combination.